diff --git a/pretext/CollectionData/Vectors.ptx b/pretext/CollectionData/Vectors.ptx
index e72e62b..80b4b88 100644
--- a/pretext/CollectionData/Vectors.ptx
+++ b/pretext/CollectionData/Vectors.ptx
@@ -1,6 +1,7 @@
 <section xml:id="collection-data_vectors">
         <title>Vectors</title>
-        <p><term>Vectors</term> are much more similar to Python lists than arrays are.
+        <introduction>
+<p><term>Vectors</term> are much more similar to Python lists than arrays are.
             Vectors use a dynamically allocated array to store their elements,
             so they can change size, and they have other friendly features as well.
             Because they use a dynamically allocated array, they use contiguous storage locations
@@ -141,7 +142,8 @@
             as we see in the next example.
             Because vectors can change size, vectors typically allocate some extra storage to accommodate for possible growth.
             Thus the vector typically has an actual <term>capacity</term> greater than the storage <term>size</term> strictly needed to contain its elements.</p>
-        <subsection xml:id="collection-data_iterating-through-vectors">
+        </introduction>
+<subsection xml:id="collection-data_iterating-through-vectors">
             <title>Iterating through Vectors</title>
             <p>When iterating vectors, you must first find the length of your container. You can simply call the <c>.length()</c> function.
                 For arrays, the number of elements can be found by getting the size in memory of the array
@@ -433,5 +435,4 @@ main()
     </exercise>
 </reading-questions>
         </subsection>
-    </section>
-
+    </section>
\ No newline at end of file